Processes are already known for the production of tetrachlorophthalonitriles, and in particular of tetrachloroisophthalonitrile. In particular, we refer to U.S. Pat. No. 3,839,401 and U.S. Pat. No. 4,485,050.
These processes, like the majority of processes based on catalytic reactions in a fluidized bed, require carrying out an optimal fluidization, especially when wishing to obtain directly products with a high degree of purity.
On the other hand, the conditions required to optimize bed fluidization do not leave much margin for the operative conditions required to run the plant.
In practice, any occasional deviations from the prefixed temperature and flow intervals lead to the formation of hypo-chlorinated and super-chlorinated impurities and, in some cases, to a rapid decay in the catalytic activity of the bed.
This may involve both a variability in product purity and higher expenses due to the costs for replacing the catalyzer and to productivity losses caused by plant stoppage.